This invention is directed to an anhydrous (2S,3S)-N-(methoxy-5-t-butylphenylmethyl-2-diphenylmethyl-1-azobicyclo[2,2 ,2] octan-3-amine citrate monohydrate salt, its single crystalline polymorphic Form A, and pharmaceutical composition containing them. The invention is also directed to a CNS active NK-1 receptor antagonist for treating emesis in a mammal including humans. Treating is defined here as preventing and treating. ##STR1##
U.S. Pat. No. 5,393,762 and U.S. Ser. No. 08/816,016, both incorporated by reference, describe pharmaceutical compositions and treatment of emesis using NK-1 receptor antagonists. The citrate monohydrate has significantly enhanced stability over other salt forms such as the benzoate which was unstable even at 5.degree. C. The mesylate form is deliquescent.